Life on earth depends on the chemical element , which is present in every living thing. Carbon is so important, it forms the basis for two branches of chemistry, organic chemistry and biochemistry. The GED will expect you to be familiar with the following terms: 

Hydrocarbons - molecules that only contain the elements carbon and hydrogen (e.g., CH₄ is a hydrocarbon while CO₂ is not).

Organic - refers to the chemistry of living things, all of which contain the element carbon.

Organic Chemistry - study of the chemistry of carbon compounds involved in life (so, studying diamond, which is a crystalline form of carbon, isn't included in organic chemistry, but studying how methane is produced is covered by organic chemistry).

Organic Molecules - molecules that have carbon atoms linked together in a straight line (carbon chain) or in a circular ring (carbon ring).

Polymer - hydrocarbons which have chained together.